There are a number of bottle capping machines currently used to apply screw caps onto bottles. In general such machines employ a reciprocating mechanism to reciprocate a screw cap applying spindle assembly through a capping cycle. A screw cap chuck, typically constructed of a tool grade steel, is attached to the spindle. These machines operate at a predetermined downward stroke while applying a pre-determined torque to the screw cap. The operating height of the chuck is usually adjustable to allow for various bottle heights.
The primary elements of the screw-on capping chuck are chuck jaws, a jaw bell, a stripper, a spring and a stem. The jaws are retained in the bell by the stem as it is acted upon by the spring. An adaptor connects the chuck to a spindle sleeve and transmits the rotary motion of the spindle sleeve. A push rod extends through the sleeve and is adapted to actuate the stripper. The chuck jaws are opened by reciprocal movement of the spindle sleeve upward forcing the stripper between the chuck jaws. The cap is then picked up by reciprocal movement of the spindle sleeve downward onto the cap which displaces the stripper, allowing the jaws to close. The cap is then screwed onto the container. When the cap has been placed on the container to a specified position, the jaws are opened to release the capped container. The jaws are opened by holding the jaw stem fixed longitudinally and moving the spindle longitudinally upward, thereby allowing the jaw bell to move longitudinally relative to the jaws. This relative movement between the jaw bell and the jaws allows the stripper to move longitudinally downward to open the jaws.
There are a number of applications for machines of this type where high speeds and precise torque are required. For example, the pharmaceutical, personal care and food industries make extensive use of these machines when packaging products for distribution. Chucks have required a substantial amount of force to be transferred through many components. The many components through which the force has to be transferred cause an increase in the time it takes to separate the chuck from the cap. This slower separation causes slipping of the jaws on the cap contributing to premature jaw wear. The magnitude of the force required also causes premature jaw wear.
Chucks made in accordance with the prior art are limited in the size of the caps they can apply, due to how wide the jaws can be opened for large caps, which require a larger jaw opening capability. In order to open wide enough to separate from larger caps, chucks of the prior art must be raised higher. Some capping machines do not have sufficient vertical space available to allow the chucks made in accordance with the prior art to be raised high enough.
Thus there exists a need for a chuck apparatus for a capping machine which permits quick, efficient and convenient acquisition and holding of small and large caps, followed by release of the cap using minimal force thereby reducing wear of chuck components.